Optical data storage disks have gained widespread acceptance for the storage, distribution and retrieval of large volumes of information. Optical data storage disks include, for example, audio CD (compact disc), CD-R(CD-recordable), CD-RW (CD-rewritable) CD-ROM (CD-read only memory), DVD (digital versatile disk or digital video disk), DVD-RAM (DVD-random access memory), and various other types of writable or rewriteable media, such as magneto-optical (MO) disks, phase change optical disks, and others. Some newer formats for optical data storage disks are progressing toward smaller disk sizes and increased data storage density. For example, some new media formats boast improved track pitches and increased storage density using blue-wavelength lasers for data readout and/or data recording.
Optical data storage disks are typically produced by first making a data storage disk master that has a surface relief pattern that represents encoded data or tracking control information on the master surface. The surface relief pattern, for instance, may be a collection of grooves or pits and lands, typically arranged in either a spiral or concentric manner. The master is typically not suitable as a mass replication surface with the master features defined within an etched photoresist layer formed over a master substrate.
After creating a suitable master, that master can be used to make a replica or a stamper, which is less fragile than the master. The stamper is typically formed of electroplated metal, and has a surface relief pattern that is the inverse of the surface relief pattern encoded on the master. If the master is originally defined to have an inverse of a desired replica pattern, the master may be used to create a first generation hard plastic replica, which is in turn used to create a second generation electroplated metal stamper that can be used to create the replica disks. An injection mold can use the electroplated metal stamper to replicate large quantities of disks. Also, photopolymer replication processes, such as rolling bead processes, have been used to replicate disks using stampers. In any case, each replica disk may contain the data and tracking information that was originally encoded on the master surface and preserved in the stamper. The replica disks can be coated with a reflective layer and/or a phase change layer, and are often sealed with an additional protective layer.
Blue disk media formats, such as Blu-Ray and High Definition Digital Versatile Disk (HD-DVD), may also use similar mastering-stamping techniques. The blue disk media formats may be compatible with a blue-laser drive head that operates at a wavelength of approximately 405 nm. As used herein, the term blue disk media (or blue disks) refers to optical disk media having a data storage capacity of greater than 15 gigabytes (GB) per data storage layer of the disk. The blue disk media formats include optically transmissive cover layers bonded over the optical disk with different thicknesses specified by the different blue disk media formats.